Systems, devices, and methods for photonic to radio frequency downconversion

ABSTRACT

A system, method, and device for RF upconversion. The system can include a laser, two EAMs, a photonic filter, a photonic service filter, two photodiodes, and a mixer. The first EAM can convert a received RF signal into the photonic domain by modulating an optical signal (received from the laser) based on the received RF signal to output a modulated optical signal. The photonic filter can output a filtered optical signal based on the modulated optical signal to the first photodiode which can output a filtered RF signal in the RF domain. The second EAM can output an LO modulated optical signal based on a received LO to the service filter which can output a filtered LO optical signal to the second photodiode which can output a filtered LO signal in the RF domain. The mixer can mix the filtered RF and LO signals to generate an IF signal.

Embodiments relate generally to systems, devices, and methods forphotonic conversion and, more particularly, to systems, devices, andmethods for photonic to radio frequency (RF) up/down conversion.

Broadband transmitters/receivers (up/down-converters) require frequencyconversion between baseband/carrier signals to transmit information fora variety of communication and/or military applications. Frequencyconversion can create spurs and harmonic products as undesirable sideeffects of the conversion process. To remove these frequency productscostly and large filter banks have been utilized in broadbandapplications. Some tunable filter methods using micro-electro-mechanicalsystems (MEMS), single crystal ferrimagnetic garnets (YIG), or varioustransducer technologies have been unable to provide a fast tuning highrejection solution. Photonic to RF conversion technology is able toadaptively filter input RF signals, removing unwanted spurious andinterfering products, and may replace traditional superhetrodyne RFfrequency conversion architectures. However, existing frequencyconversion systems that employ photonic to RF conversion technologypresent a relatively high conversion loss. There may be a need to applyphotonic to RF conversion to adaptively filter RF signals without arelatively high conversion loss.

One embodiment includes a system for RF upconversion. The system cancomprise a laser, a local oscillator, first and secondelectro-absorption modulators, a photonic filter, a photonic servicefilter, first and second photodiodes, and an RF mixer. The firstelectro-absorption modulator can be coupled to the laser to receive anoptical signal from the laser. The first electro-absorption modulatorcan be configured to convert a received RF signal into the photonicdomain by modulating the received optical signal based on the receivedRF signal to output a modulated optical signal. The photonic filter canbe coupled to the first electro-absorption modulator to receive themodulated optical signal output by the first electro-absorptionmodulator. The photonic filter can be configured to output a filteredoptical signal based on the received modulated optical signal. The firstphotodiode can be coupled to the photonic filter to receive the filteredoptical signal from the photonic filter, and can be configured toconvert the filtered optical signal into the RF domain to output afiltered RF signal. The second electro-absorption modulator can becoupled to the laser to receive the optical signal from the laser andcan be coupled to the local oscillator to receive a LO signal from thelocal oscillator. The second electro-absorption modulator can beconfigured to convert the LO signal into the photonic domain bymodulating the received optical signal based on the received LO signalto output an LO modulated optical signal. The photonic service filtercan be coupled to the second electro-absorption modulator to receive theLO modulated optical signal output by the second electro-absorptionmodulator, and can be configured to output a filtered LO optical signalbased on the received LO modulated optical signal. The second photodiodecan be coupled to the photonic service filter to receive the filtered LOoptical signal from the photonic service filter, and can be configuredto convert the filtered LO optical signal into the RF domain to output afiltered LO signal. The RF mixer can be coupled to the first and secondphotodiodes to receive the filtered RF signal from the first photodiodeand the filtered LO signal from the second photodiode, and can beconfigured to mix the filtered RF signal and the filtered LO signal todownconvert the filtered output and generate an intermediate frequency(IF) signal.

Another embodiment includes a device for RF upconversion. The device cancomprise a photonic conversion stage, a photonic filter stage, an RFconversion stage, and an RF mixer stage. The photonic conversion stagecan be coupled to a laser to receive an optical (FL) signal from thelaser. The photonic conversion stage can be configured to convert areceived RF signal to an optical signal and output the converted opticalsignal by modulating the received FL signal based on the received RFsignal in a first optical signal processing path, and, in a secondoptical signal processing path, to convert a received local oscillator(LO) signal to an optical LO signal and output the converted optical LOsignal by modulating the received FL signal based on the received LOsignal. The photonic filter stage can be coupled to the photonicconversion stage to receive from the photonic conversion stage theconverted optical signal and the converted optical LO signal, thephotonic filter stage being configured to output a filtered opticalsignal by filtering the received converted optical signal in the firstoptical signal processing path, and, in the second optical signalprocessing path, to output a filtered optical LO signal by filtering thereceived converted optical LO signal. The RF conversion stage can becoupled to the photonic filter stage to receive the filtered opticalsignal and the filtered optical LO signal from the photonic filterstage. The RF conversion stage can be configured to convert the filteredoptical signal to a filtered RF signal in the first optical signalprocessing path, and, in the second optical signal processing path, toconvert the filtered optical LO signal to a filtered LO signal. Themixer stage can be coupled to the RF conversion stage to receive thefiltered RF signal and the filtered LO signal, and can be configured tomix the filtered RF signal and the filtered LO signal to downconvert thefiltered output and generate an intermediate frequency (IF) signal.

Another embodiment can include a method for RF upconversion. The methodcan comprise receiving an RF signal. In a first optical signalprocessing path, an optical signal generated by a laser can be modulatedbased on the received RF signal to generate a modulated optical signal.The modulated optical signal can be filtered in the first optical signalprocessing path to remove undesired spurious/interfering products togenerate a filtered optical signal. The filtered optical signal can, inthe first optical signal processing path, be converted to the RF domainto generate a filtered RF signal. In a second optical signal processingpath, the optical signal generated by the laser can be modulated basedon a local oscillator (LO) signal to generate a modulated optical LOsignal. In the second optical signal processing path the modulatedoptical LO signal can be filtered to generate a filtered optical LOsignal which can then be converted to the RF domain to generate afiltered LO signal. The filtered RF signal and the filtered LO signalcan be mixed in the RF domain to downconvert the filtered output andgenerate an intermediate frequency (IF) signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a photonic to RF converter (PRFC)upconverter, in accordance with an embodiment of the present disclosure.

FIG. 2 is a functional block diagram of a PRFC upconverter, inaccordance with an embodiment of the present disclosure.

FIG. 3 is a schematic diagram of a PRFC downconverter, in accordancewith an embodiment of the present disclosure.

FIG. 4 is a functional block diagram of a PRFC downconverter, inaccordance with an embodiment of the present disclosure.

FIG. 5 is a flowchart showing a method for photonic to RF upconversion,in accordance with an embodiment of the present disclosure.

FIG. 6 is a flowchart showing a method for photonic to RFdownconversion, in accordance with an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a photonic to RF converter (PRFC)upconverter 100, in accordance with an embodiment of the presentdisclosure. PRFC upconverter 100 includes a local oscillator 104, amixer 106, an electro-absorption modulator (or “EAM”) 108, anelectro-absorption modulator (or “EAM”) 109, a thermal platform 112which includes a filter (e.g., a 5-pole Fabry-Perot (FP) filter) 114 anda service filter 116, a controller (or “locking photodiode (PD) andlaser power controller”, or “locking PD and control circuit”) 118, aterminator 120, a combiner 124, a balanced photodiode (PD) 122, a laser110, a splitter 126, a splitter 128, and a mirror 130.

In operation, local oscillator 104 generates a local oscillator (LO)signal which is mixed with an IF signal of interest 102 is at mixer 106.Mixer 106 outputs a mixed signal to EAM 108. Laser 110 outputs anoptical signal (FL) that is split by splitter 126 to EAM 108 andsplitter 128. Splitter 128 further splits FL to EAM 109 and mirror 130.Mirror 130 reflects FL to combiner 124. EAM 108 receives FL and themixed signal output by mixer 106, modulates FL based on the mixedsignal, and outputs a modulated optical signal to filter 114. Filter 114adaptively filters the received modulated optical signal to, forexample, remove unwanted spurious and/or interfering products, andoutputs a filtered optical signal to combiner 124. Combiner 124 outputsthe filtered optical signal and FL (reflected by mirror 130) to balancedPD 122 which subtracts the signals from each other and generates anoutput RF signal. EAM 109 receives FL (from splitter 128) and LO (fromlocal oscillator 104), modulates FL based on LO, and outputs an LOmodulated optical signal to service filter 116 which then outputs asignal to controller 118 which can adaptively control laser 110 based onthe signal received from service filter 116. Service filter 116discriminates, for example, the product of the laser carrier and LO withsufficient selectivity to enable laser frequency control and/or locking.

Embodiments employ photonic to RF conversion to adaptively filter inputRF signals such as, for example, IF 102 and RF 302 shown in FIG. 3below, removing unwanted spurious and interfering products. Someembodiments can be provided in a smaller package than other devicesstudied by the inventors that use switched filter banks, with moreflexibility allowing for a SWAP-C (size, weight, power, and cost)improvement over such devices. Embodiments are able to provide singlestage un-ambiguous conversion eliminating the need for a second mixingstage and associated frequency ambiguity issues encountered in otherbroad-band superhetrodyne up/down conversion systems studied by theinventors. Also, embodiments can apply filtering to the local oscillatorsource such as, for example, local oscillators 104 and 308, eliminatingthe need for high spur and harmonic suppression synthesizers seen indevices studied by the inventors, which can reduce system cost and alsoreduce size/weight considerations. Embodiments reduce conversion loss byreducing the number of RF to photonic conversion stages used in theupconversion process. The number of RF to photonic conversion stages canbe reduced by using a mixer such as, for example, mixer 106 or a mixerand a broadband amplifier before the adaptive filtering stage(eliminating, for example, a weak optical hetrodyne stage used in otherdevices studied by the inventors such as those in which conversion isself-contained in the photonic domain). This allows embodiments to takefull advantage of the adaptive filtering of the LO and RF input withoutthe high conversion loss which may be associated with photonicconversion.

In some devices studied by the inventors, conversion is self-containedin the photonic domain leading to high conversion losses. Additionally,devices/methods of tunable filtering studied by the inventors sufferfrom large size, poor filter rejection, limited bandwidth, poorreliability, and/or slow tuning times. Embodiments filter undesirableproducts of frequency conversion (e.g., spurs and harmonic products)adaptively without the normal trade-offs associated with tunablefilters, while providing, in some embodiments, a space saving solutionideally suited for compact platforms. Embodiments provide a hybridsolution of semiconductor and photonic technology that can moveseamlessly between the optical and RF domains, which allows for theadvantages of both technologies (low conversion loss and adaptivefiltering) to be utilized effectively. The losses associated withphotonic conversion devices/methods studied by the inventors can bereduced by this hybrid approach which increases conversion gain and/orreduces conversion loss.

It will be appreciated that filter 114 can be a photonic filter such as,for example, any microwave photonic filter including, for example, a5-pole Fabry-Perot (FP) microwave photonic filter. Additionally oralternatively, filter 114 can comprise filters such as, for example, afiber Bragg gratings (FBG) filter, whispering-gallery-mode (WGM)resonator filters, etalons, and/or Lyot filters.

It will also be appreciated that mixer 106 can be any kind of mixer orfrequency mixer comprising, for example, Schottky diodes, galliumarsenide field-effect transistor (GaAs FETs), complementarymetal-oxide-semiconductor (CMOS) transistors, and/or any othernon-linear element.

Although not shown, some embodiments are configured to perform adaptiveequalization of PRFC upconverter 100 according to, for example, theadaptive equalization detailed in U.S. patent application Ser. No.14/630,638, filed Feb. 24, 2015, which is hereby incorporated byreference herein in its entirety. Some such embodiments include a systemsuch as system 100 of the '638 application to perform adaptiveequalization of PRFC upconverter 100. In some embodiments, PRFCupconverter 100 is coupled to an EAM bias controller such as the EAMbias controller 114/308 of the '638 application. In some embodiments,controller 118 is configured as the EAM bias controller 114/308 of the'638 application.

In some embodiments, PRFC upconverter 100 includes a thermoelectriccooler (not shown). Although not shown, some embodiments are configuredto adaptively control the thermoelectric cooler of PRFC upconverter 100and/or laser 110 to maintain precise operation of laser 110 accordingto, for example, the adaptive control detailed in U.S. patentapplication Ser. No. 14/630,639, filed Feb. 24, 2015, which is herebyincorporated by reference herein in its entirety. Some such embodimentsinclude a system such as system 100 of the '639 application to maintainprecise operation of laser 110 of PRFC upconverter 100. In someembodiments, PRFC upconverter 100 is coupled to a laser power controllersuch as the laser power controller 116 of the '639 application. In someembodiments, controller 118 is configured as the laser power controller116 of the '639 application. In some embodiments, PRFC upconverter 100is coupled to a thermoelectric cooler controller such as the TECcontroller 110 of the '639 application.

FIG. 2 is a functional block diagram of a PRFC upconverter 200, inaccordance with an embodiment of the present disclosure. PRFCupconverter 200 includes an RF mixer stage 202, a photonic conversionstage (or “RF to photonic conversion stage”) 204, a photonic adaptivefiltering stage 206, and an RF conversion stage (or “photonic to RFconversion stage”) 206.

Mixer stage 202 can be coupled to a local oscillator to receive a localoscillator (LO) signal form the local oscillator. The mixer stage 202can be configured to mix an intermediate frequency (IF) signal with thereceived LO signal to output a mixed RF signal. Photonic conversionstage 204 can be coupled to mixer stage 202 to receive the mixed RFsignal from mixer stage 202. Photonic conversion stage 204 can also becoupled to a laser to receive an optical (FL) signal from the laser.Photonic conversion stage 204 can be configured to, for a first opticalsignal processing path, convert the received mixed RF signal to anoptical signal and output the converted optical signal by modulating thereceived FL signal based on the received mixed RF signal. Photonicfilter stage 206 can be coupled to photonic conversion stage 204 toreceive the converted signal from photonic conversion stage 204.Photonic filter stage 206 can also be configured to filter the convertedoptical signal to, for example, remove unwanted spurious and/orinterfering products from the converted optical signal, and output afiltered signal. RF conversion stage 208 can be coupled to photonicfilter stage 206 to receive the filtered signal from photonic filterstage 206 and output an upconverted RF signal by converting the receivedfiltered signal to the RF domain.

In some embodiments, photonic conversion stage 204 can be configured to,for a second separate optical signal processing path, receive the LO andFL signals and convert the LO signal to an optical LO signal and outputthe converted LO optical signal by modulating the received FL signalbased on the received LO signal. In such embodiments, the photonicfilter stage 206 can receive the converted LO optical signal fromphotonic conversion stage 204. In such embodiments, PRFC upconverter 200can include acontroller configured to control the laser based on asignal received from photonic filter stage 206 (the signal received fromphotonic filter stage 206 being based on the converted LO optical signalsuch as, for example, the converted LO optical signal reflected byphotonic filter stage 206).

In some embodiments mixer stage 202 can include a mixer such as, forexample, mixer 106, the first optical signal processing path of photonicconversion stage 204 can include an optical modulator such as, forexample, EAM 108, photonic filter stage 206 can include a filter suchas, for example, filter 114, and RF conversion stage 208 can include aphotodiode such as, for example, photodiode 122.

In some embodiments, the second optical signal processing path ofphotonic conversion stage 204 can include a second EAM such as, forexample, EAM 109 and photonic filter stage 206 can also include a secondfilter such as, for example, service filter 116.

In some embodiments, a baseband amplifier stage is included beforephotonic conversion stage 206 and/or photonic filter stage 208. Byapplying RF mixer stage 204 and/or the amplifier stage in the RF (e.g.,microwave) domain prior to photonic filter stage 208, embodiments caneliminate a weak optical heterodyne stage included in systems studied bythe inventors in which all conversion is self-contained in the photonicdomain. Such a weak optical heterodyne stage can lead to high conversionlosses and by eliminating this stage embodiments provide photonicadaptive filtering without the high conversion losses associated withsuch weak optical heterodyne stages.

FIG. 3 is a schematic diagram of a PRFC downconverter 300, in accordancewith an embodiment of the present disclosure. PRFC downconverter 300includes a laser 304, an electro-absorption modulator (EAM) 306, anelectro-absorption modulator (EAM) 307, a local oscillator 308, athermal platform 310 including a filter (or “5-pole FP filter”) 312 anda service filter 314, a controller (or “locking photodiode (PD) andlaser power controller”, or “locking PD and control circuit”) 316,photodiodes (PDs) 320 and 322, bandpass filter 326, splitters 328-332,combiners 338-340, and mirror 334.

In operation, laser 304 outputs an optical signal (FL) to splitter 328which splits FL to EAM 306 and splitter 330. Splitter 330 further splitsFL to EAM 307 and splitter 332. Splitter 332 further splits FL tocombiner 340 and mirror 334 which reflects FL to combiner 338. EAM 306converts RF signal 302 into an optical signal by modulating the FLsignal based on the received RF signal 302 to output a modulated FLsignal to filter 312. Filter 312 filters the modulated FL signal to, forexample, remove unwanted spurious and/or interfering products, andoutputs a filtered optical signal to combiner 338. Combiner 338 outputsthe filtered optical signal and the FL signal (received from mirror 334)to photodiode 320 which subtracts the FL signal from the filteredoptical signal and converts the result to a filtered RF signal in the RFdomain which is output to mixer 324.

In a second optical signal processing path, EAM 307 converts an LOsignal received from local oscillator 308 to a converted LO opticalsignal by modulating the FL signal based on the LO signal to output anLO modulated FL signal to service filter 314. Service filter 314 canoutput a signal to controller 316 which can adaptively control laser 304based on the signal received from service filter 314. Service filter 314can output a signal based on the LO modulated FL signal to combiner 340.Combiner 340 outputs the signal received from service filter 314 and theFL signal (received from splitter 332) to photodiode 322 which subtractsthe signals and converts the result to a filtered LO signal in the RFdomain which is output to mixer 324. Mixer 324 mixes the signalsreceived from PD 320 and PD 322 and outputs a mixed RF signal bandpassfilter 326 which outputs an intermediate frequency (IF) signal.

In embodiments, mixer 324 is an RF (e.g., microwave) mixer, and by usingmixer 324 after the adaptive photonic filtering, such embodiments caneliminate a weak optical heterodyne stage included in systems studied bythe inventors in which all conversion is self-contained in the photonicdomain. Such a weak optical heterodyne stage can lead to high conversionlosses and by eliminating this stage (by reducing the number of RF tophotonic conversion stages) embodiments provide photonic adaptivefiltering without the high conversion losses associated with such a weakoptical heterodyne stage.

It will be appreciated that filter 312 can be a photonic filter such as,for example, any microwave photonic filter including, for example, a5-pole Fabry-Perot (FP) microwave photonic filter.

It will also be appreciated that mixer 324 can be any kind of mixer orfrequency mixer comprising, for example, Schottky diodes, galliumarsenide field-effect transistor (GaAs FETs), complementarymetal-oxide-semiconductor (CMOS) transistors, and/or the like.

Although not shown, some embodiments are configured to perform adaptiveequalization of PRFC downconverter 300 according to, for example, theadaptive equalization detailed in U.S. patent application Ser. No.14/630,638, filed Feb. 24, 2015, which has been incorporated byreference herein in its entirety. Some such embodiments include a systemsuch as system 100 of the '638 application to perform adaptiveequalization of PRFC downconverter 300. In some embodiments, PRFCdownconverter 300 is coupled to an EAM bias controller such as the EAMbias controller 114/308 of the '638 application. In some embodiments,controller 316 is configured as the EAM bias controller 114/308 of the'638 application.

In some embodiments, PRFC downconverter 300 includes a thermoelectriccooler (not shown). Although not shown, some embodiments are configuredto adaptively control the thermoelectric cooler of PRFC downconverter300 and/or laser 304 to maintain precise operation of laser 304according to, for example, the adaptive control detailed in U.S. patentapplication Ser. No. 14/630,639, filed Feb. 24, 2015, which has beenincorporated by reference herein in its entirety. Some such embodimentsinclude a system such as system 100 of the '639 application to maintainprecise operation of laser 304 of PRFC downconverter 300. In someembodiments, PRFC downconverter 300 is coupled to a laser powercontroller such as the laser power controller 116 of the '639application. In some embodiments, controller 316 is configured as thelaser power controller 116 of the '639 application. In some embodiments,PRFC downconverter 300 is coupled to a thermoelectric cooler controllersuch as the TEC controller 110 of the '639 application.

FIG. 4 is a functional block diagram of a PRFC downconverter 400, inaccordance with an embodiment of the present disclosure. PRFCdownconverter 400 includes photonic conversion stage 402, a photonicadaptive filtering stage 404, an RF conversion stage 406, and a mixerstage 408.

Photonic conversion stage 402 can, in a first optical signal processingpath, convert an input RF signal into an optical signal by modulating anoptical (FL) signal (generated by a laser) based on the RF signal.Photonic filter stage 404 can be coupled to photonic conversion stage402 to receive the converted/modulated optical signal. Photonic filterstage 404 can be configured to filter the converted optical signal to,for example, remove unwanted spurious and/or interfering products fromthe converted optical signal, and output a filtered optical signal to RFconversion stage 406 which converts the filtered optical signal into anRF filtered signal.

In a second optical processing path, photonic conversion stage 402 canreceive a local oscillator (LO) signal and the FL signal and convert theLO signal to an optical LO signal by modulating the FL signal based onthe LO signal. Photonic filter stage 404 can receive the optical LOsignal from photonic conversion stage 402 and output a signal based onthe optical LO signal to a controller that can control the laser (e.g.,frequency) based on the feedback provided by photonic filter stage 404.Photonic filter stage 404 can also output a signal based on the opticalLO signal to RF conversion stage 406 which converts the signal into anLO filtered signal in the RF domain.

RF mixer stage 408 receives the LO filtered signal and the RF filteredsignal from RF conversion stage 406, mixes the signals in the RF domain,and outputs an intermediate frequency (IF) signal.

In some embodiments, in the first optical signal processing path,photonic conversion stage 402 can include an optical modulator such as,for example, EAM 306, photonic filter stage 404 can include a filtersuch as, for example, filter 312, and RF conversion stage 406 caninclude a photodiode such as, for example, photodiode 320. In someembodiments, in the second optical signal processing path, photonicconversion stage 402 can include a second EAM such as, for example, EAM307, photonic filter stage 404 can include a second filter such as, forexample, service filter 314, and RF conversion stage 406 can include asecond photodiode such as, for example, photodiode 322. In someembodiments mixer stage 408 can include a mixer such as, for example,mixer 324. In some embodiments, although not shown, a bandpass filterstage is included after RF mixer stage 408.

By separating optical signal processing into two paths, filtering the RFand the LO signals separately in each path, and applying RF mixer stage408 in the RF (e.g., microwave) domain after photonic filter stage 208,embodiments can eliminate a weak optical heterodyne stage included insystems studied by the inventors in which all conversion isself-contained in the photonic domain. Such a weak optical heterodynestage can lead to high conversion losses and by eliminating this stageembodiments provide photonic adaptive filtering without the highconversion losses associated with such weak optical heterodyne stages.

FIG. 5 is a flowchart showing a method 500 for photonic to RFupconversion, in accordance with an embodiment of the presentdisclosure. Processing begins at 502 and continues to 504.

At 504, an IF signal of interest is received. Processing continues to506.

At 506, a local oscillator (LO) signal is generated. Processingcontinues to 508.

At 508, the IF and LO signals are mixed at a mixer such as, for example,mixer 106. Processing continues to 510.

At 510, a laser (LF) is generated. Signal processing cab be separatedinto two paths and processing continues to 512 and 514. In someembodiments, amplification can be performed in the microwave domain by,for example, a baseband amplifier, prior to photonic adaptive filtering.

At 512, photonic conversion is performed by modulating the LF signalbased on the output from the mixer to generate a converted/modulatedoptical signal. Photonic conversion can be performed by anelectro-absorption modulator such as, for example, EAM 108. Processingcontinues to 514.

At 514, adaptive filtering is performed in the photonic domain. Adaptivefiltering can be performed by a photonic filter such as, for example,filter 114, on the converted/modulated optical signal output by theelectro-absorption modulator at 512 to, for example, remove unwantedspurious and/or interfering products from the converted/modulatedoptical signal. Processing continues to 516.

At 516, upconverted RF output is generated based on the filtered opticalsignal. Generating upconverted RF output can be performed by a combinersuch as, for example, combiner 124 and a photodiode such as, forexample, photodiode 122. The combiner can receive the FL signal andcombine the FL signal and the filtered optical signal and output thesignals to the photodiode which can subtract the signals and convert theresult to an upconverted RF signal in the RF domain.

At 518, photonic conversion is performed by modulating the LF signalbased on the LO signal to generate an LO modulated optical signal. Thisphotonic conversion can be performed by an electro-absorption modulatorsuch as, for example, EAM 109. Processing continues to 520.

At 520, service filtering is performed in the photonic domain.Processing continues to 522.

At 522, laser adjustment is performed based on an output of the servicefiltering at 520. Laser adjustment can be performed by a controller suchas, for example, controller 118. In some embodiments, laser adjustmentcan maintain transmission of agile sideband through active feedback toadjust laser carrier frequency. Processing continues to 524, whereprocessing ends.

It will be appreciated that operations 504-522 may be repeated in wholeor in part to perform continuous photonic to RF upconversion.

FIG. 6 is a flowchart showing a method 600 for photonic to RFdownconversion, in accordance with an embodiment of the presentdisclosure. Processing begins at 602 and continues to 604.

At 604, an RF signal including a signal of interest (SOI) is received.Processing continues to 606.

At 606, a local oscillator (LO) signal is generated. Processingcontinues to 608.

At 608, a laser (LF) is generated. Optical signal processing isseparated into two separate paths and processing continues to 610 and616.

At 610, photonic conversion is performed by modulating the LF signalbased on the RF signal to generate a converted/modulated optical signal.Photonic conversion can be performed by an electro-absorption modulatorsuch as, for example, EAM 306. Processing continues to 612.

At 612, adaptive filtering is performed in the photonic domain. Adaptivefiltering can be performed by a photonic filter such as, for example,filter 312, on the converted/modulated optical signal output by theelectro-absorption modulator at 610 to, for example, remove unwantedspurious and/or interfering products from the converted/modulatedoptical signal. Processing continues to 614.

At 614, RF conversion is performed to convert the filtered opticalsignal generated at 612 into a filtered RF signal in the RF domain.Processing continues to 622.

At 616, photonic conversion is performed by modulating the LF signalbased on the LO signal to generate an LO converted/modulated opticalsignal. This photonic conversion can be performed by anelectro-absorption modulator such as, for example, EAM 307. Processingcontinues to 618.

At 618, service filtering is performed in the photonic domain. Theservice filtering can be performed by a filter such as, for example,service filter 314. In some embodiments, laser adjustment is performedbased on an output of the service filtering at 618. Laser adjustment canbe performed by a controller such as, for example, controller 316. Insome embodiments, laser adjustment can maintain transmission of agilesideband through active feedback to adjust laser carrier frequency.Processing continues to 620.

At 614, RF conversion is performed to convert the filtered LO opticalsignal generated at 618 into a filtered LO signal in the RF domain.Processing continues to 622.

At 622, the filtered RF signal and the filtered LO signals are mixed ata mixer. The signals can be mixed by a mixer such as, for example, mixer324 and then filtered by a filter such as bandpass filter 326 todownconvert the filtered output. Processing continues to 624.

At 618, the downconverted filtered output is output as the intermediatefrequency (IF) signal, where processing ends.

It will be appreciated that operations 604-624 may be repeated in wholeor in part (an example of which is indicated by line 614) to maintaincurrent (regularly or continuously updated).

It will be appreciated that the modules, processes, systems, andsections described above can be implemented in hardware, hardwareprogrammed by software, software instructions stored on a nontransitorycomputer readable medium or a combination of the above. A system forphotonic to RF up/down conversion, for example, can include using aprocessor configured to execute a sequence of programmed instructionsstored on a nontransitory computer readable medium. For example, theprocessor can include, but not be limited to, a personal computer orworkstation or other such computing system that includes a processor,microprocessor, microcontroller device, or is comprised of control logicincluding integrated circuits such as, for example, an ApplicationSpecific Integrated Circuit (ASIC). The instructions can be compiledfrom source code instructions provided in accordance with a programminglanguage such as C, Ada, Java, C++, C#.net or the like. The instructionscan also comprise code and data objects provided in accordance with, forexample, the Visual Basic™ language, or another structured orobject-oriented programming language. The sequence of programmedinstructions and data associated therewith can be stored in anontransitory computer-readable medium such as a computer memory orstorage device which may be any suitable memory apparatus, such as, butnot limited to ROM, PROM, EEPROM, RAM, flash memory, disk drive and thelike.

Furthermore, the modules, processes systems, and sections can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned above may beperformed on a single or distributed processor (single and/ormulti-core, or cloud computing system). Also, the processes, systemcomponents, modules, and sub-modules described in the various figures ofand for embodiments above may be distributed across multiple computersor systems or may be co-located in a single processor or system.Exemplary structural embodiment alternatives suitable for implementingthe modules, sections, systems, means, or processes described herein areprovided below.

The modules, processors or systems described above can be implemented asa programmed general purpose computer, an electronic device programmedwith microcode, a hard-wired analog logic circuit, software stored on acomputer-readable medium or signal, an optical computing device, anetworked system of electronic and/or optical devices, a special purposecomputing device, an integrated circuit device, a semiconductor chip,and a software module or object stored on a computer-readable medium orsignal, for example.

Embodiments of the method and system (or their sub-components ormodules), may be implemented on a general-purpose computer, aspecial-purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hardwired electronic or logiccircuit such as a discrete element circuit, a programmed logic circuitsuch as a PLD, PLA, FPGA, PAL, or the like. In general, any processorcapable of implementing the functions or steps described herein can beused to implement embodiments of the method, system, or a computerprogram product (software program stored on a nontransitory computerreadable medium).

Furthermore, embodiments of the disclosed method, system, and computerprogram product may be readily implemented, fully or partially, insoftware using, for example, object or object-oriented softwaredevelopment environments that provide portable source code that can beused on a variety of computer platforms. Alternatively, embodiments ofthe disclosed method, system, and computer program product can beimplemented partially or fully in hardware using, for example, standardlogic circuits or a VLSI design. Other hardware or software can be usedto implement embodiments depending on the speed and/or efficiencyrequirements of the systems, the particular function, and/or particularsoftware or hardware system, microprocessor, or microcomputer beingutilized. Embodiments of the method, system, and computer programproduct can be implemented in hardware and/or software using any knownor later developed systems or structures, devices and/or software bythose of ordinary skill in the applicable art from the functiondescription provided herein and with a general basic knowledge of thecomputer programming and network security arts.

Moreover, embodiments of the disclosed method, system, and computerprogram product can be implemented in software executed on a programmedgeneral purpose computer, a special purpose computer, a microprocessor,or the like.

It is, therefore, apparent that there is provided, in accordance withthe various embodiments disclosed herein, systems, devices, and methodsfor photonic to RF up/down conversion.

While the invention has been described in conjunction with a number ofembodiments, it is evident that many alternatives, modifications andvariations would be or are apparent to those of ordinary skill in theapplicable arts. Accordingly, Applicants intend to embrace all suchalternatives, modifications, equivalents and variations that are withinthe spirit and scope of the invention.

What is claimed is:
 1. A communication device for radio frequency (RF)downconversion, the communication device comprising: a laser; a localoscillator; a first electro-absorption modulator coupled to the laser toreceive an optical signal from the laser, the first electro-absorptionmodulator configured to convert a received RF signal into the photonicdomain by modulating the received optical signal based on the receivedRF signal to output a modulated optical signal; a photonic filtercoupled to the first electro-absorption modulator to receive themodulated optical signal output by the first electro-absorptionmodulator, the photonic filter being configured to output a filteredoptical signal based on the received modulated optical signal; a firstphotodiode coupled to the photonic filter to receive the filteredoptical signal from the photonic filter, the first photodiode beingconfigured to convert the filtered optical signal into the RF domain tooutput a filtered RF signal; a second electro-absorption modulatorcoupled to the laser to receive the optical signal from the laser andcoupled to the local oscillator to receive a LO signal from the localoscillator, the second electro-absorption modulator configured toconvert the LO signal into the photonic domain by modulating thereceived optical signal based on the received LO signal to output an LOmodulated optical signal; a photonic service filter coupled to thesecond electro-absorption modulator to receive the LO modulated opticalsignal output by the second electro-absorption modulator, the photonicservice filter being configured to output a filtered LO optical signalbased on the received LO modulated optical signal; a second photodiodecoupled to the photonic service filter to receive the filtered LOoptical signal from the photonic service filter, the second photodiodebeing configured to convert the filtered LO optical signal into the RFdomain to output a filtered LO signal; an RF mixer coupled to the firstand second photodiodes to receive the filtered RF signal from the firstphotodiode and the filtered LO signal from the second photodiode, the RFmixer configured to mix the filtered RF signal and the filtered LOsignal to downconvert filtered output and generate an intermediatefrequency (IF) signal.
 2. The device of claim 1, further comprising: alocking photodiode and laser power controller coupled to the photonicservice filter to receive a reflected signal based on the LO modulatedoptical signal from the photonic service filter, the controller alsobeing coupled to the laser to control the laser to perform a laseradjustment based on the reflected signal received form the photonicservice filter, wherein the photonic filter is centered on sideband bythe laser adjustment.
 3. The device of claim 1, further comprising: afirst combiner coupled to the photonic filter to receive the filteredoptical signal from the photonic filter, coupled to the laser to receivethe optical signal from the laser, and coupled to the first photodiodeto output a signal based on the filtered optical signal and the opticalsignal; and a second combiner coupled to the photonic service filter toreceive the filtered LO optical signal from the photonic filter, coupledto the laser to receive the optical signal from the laser, and coupledto the second photodiode to output a signal based on the filtered LOoptical signal and the optical signal.
 4. The device of claim 1, whereinthe RF mixer is a microwave RF mixer.
 5. The device of claim 4, whereinthe photonic filter is a microwave photonic filter.
 6. The device ofclaim 5, wherein the photonic filter is a Fabry-Pérot filter.
 7. Thedevice of claim 6, wherein the photonic filter is a five poleFabry-Pérot filter.
 8. The device of claim 6, wherein the performing alaser adjustment includes adjusting the power of the laser based on thereflected signal received form the photonic service filter.
 9. Acommunication device for radio frequency (RF) downconversion, thecommunication device comprising: a photonic conversion stage coupled toa laser to receive an optical (FL) signal from the laser, the photonicconversion stage being configured to: in a first optical signalprocessing path, convert a received RF signal to an optical signal andoutput the converted optical signal by modulating the received FL signalbased on the received RF signal, and in a second optical signalprocessing path, convert a received local oscillator (LO) signal to anoptical LO signal and output the converted optical LO signal bymodulating the received FL signal based on the received LO signal; aphotonic filter stage coupled to the photonic conversion stage toreceive from the photonic conversion stage the converted optical signaland the converted optical LO signal, the photonic filter stage beingconfigured to: in the first optical signal processing path, output afiltered optical signal by filtering the received converted opticalsignal, and in the second optical signal processing path, output afiltered optical LO signal by filtering the received converted opticalLO signal; an RF conversion stage coupled to the photonic filter stageto receive the filtered optical signal and the filtered optical LOsignal from the photonic filter stage, the RF conversion stageconfigured to: in the first optical signal processing path, convert thefiltered optical signal to a filtered RF signal, and in the secondoptical signal processing path, convert the filtered optical LO signalto a filtered LO signal; and a mixer stage coupled to the RF conversionstage to receive the filtered RF signal and the filtered LO signal, themixer stage being configured to mix the filtered RF signal and thefiltered LO signal to downconvert the filtered output and generate anintermediate frequency (IF) signal.
 10. The device of claim 9, furthercomprising: a controller coupled to the photonic filter stage to receivea signal based on the converted optical LO signal from the photonicfilter stage, the controller being further coupled to the laser tocontrol the laser to perform a laser adjustment based on the signalreceived form the photonic filter stage, wherein the photonic filterstage is centered on sideband by the laser adjustment.
 11. The device ofclaim 9, wherein the mixer stage comprises a microwave RF mixer.
 12. Thedevice of claim 11, wherein the photonic conversion stage comprises anelectro-absorption modulator.
 13. The device of claim 12, wherein thephotonic filter stage comprises a photonic microwave filter.
 14. Thedevice of claim 13, wherein the photonic microwave filter is aFabry-Pérot filter.
 15. The device of claim 13, wherein the photonicmicrowave filter is a five pole Fabry-Pérot filter.
 16. A method for RFdownconversion, the method comprising: receiving an RF signal;modulating, based on the received RF signal and in a first opticalsignal processing path, an optical signal generated by a laser togenerate a modulated optical signal; modulating, based on a localoscillator (LO) signal and in a second optical signal processing path,the optical signal generated by the laser to generate a modulatedoptical LO signal; filtering, in the first optical signal processingpath, the modulated optical signal to remove undesiredspurious/interfering products to generate a filtered optical signal;filtering, in the second optical signal processing path, the modulatedoptical LO signal to generate a filtered optical LO signal; converting,in the first optical signal processing path, the filtered optical signalto the RF domain to generate a filtered RF signal; converting, in thesecond optical signal processing path, the filtered optical LO signal tothe RF domain to generate a filtered LO signal; mixing, at a mixer, thefiltered RF signal and the filtered LO signal in the RF domain todownconvert the filtered output and generate an intermediate frequency(IF) signal.
 17. The method of claim 16, the method further comprising:controlling the laser generating the optical signal via active feedbackto perform a laser adjustment based on the modulated optical LO signalto center the filtering on sideband.
 18. The method of claim 16, whereinthe performing the laser adjustment includes adjusting the power of thelaser based on the modulated optical LO signal.
 19. The device of claim16, wherein the filtering, in the first optical signal processing path,includes filtering modulated optical signal with a photonic microwarefilter.
 20. The device of claim 16, wherein the photonic microwarefilter is a five pole Fabry-Pérot filter.